CN118005227A

CN118005227A - Method for removing radium and/or thorium by in-situ generation of hydrotalcite in waste water

Info

Publication number: CN118005227A
Application number: CN202410279622.6A
Authority: CN
Inventors: 李存增; 徐乐昌; 王亚兰; 王扬; 周磊; 吴名涛; 胡鹏华
Original assignee: Beijing Research Institute of Chemical Engineering and Metallurgy of CNNC
Current assignee: Beijing Research Institute of Chemical Engineering and Metallurgy of CNNC
Priority date: 2024-03-12
Filing date: 2024-03-12
Publication date: 2024-05-10

Abstract

The invention relates to the technical field of sewage treatment, in particular to a method for removing radium and thorium in wastewater. The invention adjusts the pH value of the wastewater to 4-10, adds insoluble divalent metal source for nucleation reaction, adds alkali metal hydroxide and soluble divalent metal source for pre-crystallization, adds soluble trivalent metal source for crystallization-adsorption complexation, and then carries out solid-liquid separation. The method for removing hydrotalcite by in-situ generation of hydrotalcite in waste water is adopted, the proper valence complex formed by thorium and radium can be directly reacted while the hydrotalcite adsorption material is generated in-situ, and simultaneously, in the process of directly synthesizing hydrotalcite in waste water, thorium and radium nuclide is easier to enter into the vacancy of hydrotalcite, and the radium removing rate is higher. In addition, compared with the method for preparing hydrotalcite and then removing thorium and radium by using hydrotalcite in situ generated in the wastewater, the method for removing the thorium and radium by using hydrotalcite in situ generated in the wastewater provided by the invention has the advantages of shorter time consumption, simpler wastewater treatment process and higher wastewater treatment efficiency.

Description

Method for removing radium and/or thorium by in-situ generation of hydrotalcite in waste water

Technical Field

The invention relates to the technical field of sewage treatment, in particular to a method for removing radium and thorium in wastewater.

Background

In recent years, the industry of various countries in the world is rapidly developed, and zirconium products are widely applied to various departments of national economy and various fields of scientific research. At present, the domestic zirconium oxychloride almost adopts the process of alkali fusion decomposition (alkali burning), water washing conversion (water conversion), acidification, water dissolution, concentration crystallization, acid washing, centrifugal dehydration and the like. The zirconium crystallization mother liquor contains metal ions such as zirconium, titanium, hafnium, scandium and the like and radioactive ions such as uranium, thorium, radium and the like. After valuable metals are extracted through membrane separation, ion exchange, extraction, precipitation and other processes, part of radioactive substances such as thorium, radium and the like are still contained in the tail solution, and in order to prevent the tail solution from producing radiation pollution to the environment, the radioactive ions of the tail solution need to be further deeply removed. The method for removing the radium and the thorium mainly comprises a precipitation method, an adsorption method, an electrochemical method and the like.

For example, chinese patent CN102336461a discloses a method for removing metal ions in aqueous solution by using hydrotalcite, 1) dissolving soluble divalent inorganic metal salt in water to prepare salt solution a, and simultaneously preparing soluble trivalent inorganic metal salt and alkali into mixed solution B, wherein the molar ratio of divalent metal ion to trivalent metal ion is 1-4.5, the molar concentration of divalent metal ion is 0.2-2.5 mol/L, the molar concentration of trivalent metal ion is 0.1-1.25 mol/L, and the molar concentration of alkali solution is 0.1-5 mol/L; 2) Adding the mixed solution B prepared in the step 1) into a reaction tank, adjusting the temperature to 10-100 ℃, adding the solution A into the reaction tank at the stirring rotation speed of 200-500 rpm, and filtering to obtain a hydrotalcite crude product after the addition is finished; 3) Washing the hydrotalcite crude product obtained after filtering in the step 2) with water, and drying to obtain dried hydrotalcite; the prepared hydrotalcite is then subjected to removal of metal ions in the aqueous solution, wherein the metal ions comprise thorium ions. However, the method needs to prepare hydrotalcite and remove thorium ions, the steps are complex, the removal rate of the thorium ions is only 90.5-92.3%, and the removal rate of the thorium ions is not high enough.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for removing radium and/or thorium by in-situ formation of hydrotalcite in wastewater. The method provided by the invention has the advantages of high removal rate of radium and thorium, simple process and high wastewater treatment efficiency.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a method for removing radium and/or thorium by in-situ generation of hydrotalcite in wastewater, which comprises the following steps:

adjusting the pH value of the wastewater to 4-10, adding an insoluble divalent metal source for nucleation reaction, then adding alkali metal hydroxide and the soluble divalent metal source for pre-crystallization, adding a soluble trivalent metal source for crystallization-adsorption complexation, and then carrying out solid-liquid separation to respectively obtain radium and/or thorium-containing solid slag and purified water.

Preferably, the thorium content in the wastewater is less than or equal to 5mg/L, and the radium content is less than or equal to 30Bq/L.

Preferably, the pH regulator used for regulating the pH value comprises one or more of sodium hydroxide, potassium hydroxide and ammonia water.

Preferably, the divalent metal ions in the insoluble divalent metal source include one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺;

the adding amount of the insoluble divalent metal source is 0.1-2 g/L.

Preferably, the nucleation reaction is carried out at a temperature of 20-50 ℃ for 1-30 min.

Preferably, the divalent metal ions in the soluble divalent metal source include one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺.

Preferably, the total addition amount of the alkali metal hydroxide and the soluble divalent metal source is 0.5-3 g/L; the mass of the alkali metal hydroxide accounts for 10-30% of the total mass of the alkali metal hydroxide and the soluble divalent metal source.

Preferably, the temperature of the pre-crystallization is 20-50 ℃ and the time is 1-30 min.

Preferably, the trivalent metal ions in the soluble trivalent metal source include one or more of Al ³⁺、Cr³⁺、Fe³⁺ and Sc ³⁺; the addition amount of the soluble trivalent metal source is 0.1-2 g/L.

Preferably, the crystallization-adsorption complexing temperature is 20-50 ℃ and the time is 10-60 min.

The invention provides a method for removing radium and/or thorium by in-situ generation of hydrotalcite in wastewater, which comprises the following steps: adjusting the pH value of the wastewater to 4-10, adding an insoluble divalent metal source for nucleation reaction, then adding alkali metal hydroxide and the soluble divalent metal source for pre-crystallization, adding a soluble trivalent metal source for crystallization-adsorption complexation, and then carrying out solid-liquid separation to respectively obtain radium and/or thorium-containing solid slag and purified water. The method for removing hydrotalcite by in-situ generation of hydrotalcite in waste water is adopted, the proper valence complex formed by thorium and radium can be directly reacted while the hydrotalcite adsorption material is generated in-situ, and simultaneously, in the process of directly synthesizing hydrotalcite in waste water, thorium and radium nuclide is easier to enter into the vacancy of hydrotalcite, and the radium removing rate is higher. In addition, compared with the method for preparing hydrotalcite and then removing thorium and radium by using hydrotalcite in situ generated in the wastewater, the method for removing the thorium and radium by using hydrotalcite in situ generated in the wastewater provided by the invention has the advantages of shorter time consumption, simpler wastewater treatment process, higher wastewater treatment efficiency and low cost. The hydrotalcite in-situ generation technology adopted by the invention can break through the single chemical reaction effect of the traditional precipitation method, and the radium and thorium nuclides are removed by complexation in the hydrotalcite generation process, and the reaction is rapid, and the radium and thorium removal and separation effects are good.

Detailed Description

The invention provides a method for removing radium and thorium by in-situ generation of hydrotalcite in wastewater, which comprises the following steps:

Unless otherwise specified, materials and equipment used in the present invention are commercially available in the art.

In the invention, the thorium content in the wastewater is preferably less than or equal to 5mg/L, more preferably 0.5-5 mg/L, and even more preferably 1-3 mg/L; the radium content in the wastewater is preferably less than or equal to 30Bq/L, more preferably 1-30 Bq/L, and even more preferably 5-20 Bq/L. The present invention is not particularly limited to the above-mentioned waste water, and may be any waste water containing radium and/or thorium known to those skilled in the art, such as zirconium oxychloride waste liquid.

In the present invention, the pH adjuster used for the pH adjustment preferably includes one or more of sodium hydroxide, potassium hydroxide and ammonia water, more preferably sodium hydroxide and/or potassium hydroxide. The amount of the pH adjustor is not particularly limited, and the pH of the wastewater may be adjusted to 4 to 10 (preferably 5 to 9, more preferably 6 to 8, still more preferably 6 to 7).

In the present invention, the divalent metal ion in the insoluble divalent metal source preferably includes one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺, more preferably Mg ²⁺ or Ca ²⁺; the anions in the insoluble divalent metal source preferably comprise carbonate or hydroxide, i.e. the insoluble divalent metal source preferably comprises divalent metal carbonate and/or divalent metal hydroxide, more preferably a mixture of divalent metal carbonate and divalent metal hydroxide, the molar ratio of divalent metal carbonate and divalent metal hydroxide in the mixture of divalent metal carbonate and divalent metal hydroxide preferably being 1-2: 1, more preferably 1 to 1.5:1, particularly preferably comprises one or more of MgCO ₃-Mg(OH)₂、CaCO₃-Ca(OH)₂. In the present invention, the amount of the insoluble divalent metal source to be added is preferably 0.1 to 2g/L, more preferably 0.2 to 1g/L, still more preferably 0.15 to 0.5g/L. The invention is beneficial to the formation of hydrotalcite structure and improves the stability thereof by adding an insoluble divalent metal source as a nucleating agent.

In the present invention, the temperature of the nucleation reaction is preferably 20 to 50 ℃, more preferably 25 to 40 ℃, still more preferably 25 to 30 ℃; the time for the nucleation reaction is preferably 1 to 30 minutes, more preferably 5 to 20 minutes, and still more preferably 10 to 15 minutes.

In the present invention, the divalent metal ion in the soluble divalent metal source preferably includes one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺, more preferably Mg ²⁺、Mn²⁺、Ni²⁺; the anions in the soluble divalent metal source preferably comprise NO ^3-、Cl^-、SO₄ ^2- or PO ₄ ^3-, i.e. the soluble divalent metal source preferably comprises one or several of divalent metal nitrate, divalent metal chloride, divalent metal sulfate and divalent metal phosphate, particularly preferably Mg (one or several of NO ₃)₂、MgCl₂、Mg₃(PO₄)₂、MnCl₂ and NiCl ₂).

In the present invention, the alkali metal hydroxide preferably includes sodium hydroxide and/or potassium hydroxide.

In the present invention, the total amount of the alkali metal hydroxide and the soluble divalent metal source added is 0.5 to 3g/L, more preferably 1 to 2.5g/L, still more preferably 1.5 to 2g/L. In the present invention, the mass of the alkali metal hydroxide is preferably 10 to 30%, more preferably 10 to 20%, and still more preferably 10 to 15% of the total mass of the alkali metal hydroxide and the soluble divalent metal source.

In the present invention, the temperature of the pre-crystallization is preferably 20 to 50 ℃, more preferably 25 to 40 ℃, still more preferably 25 to 30 ℃; the time for the pre-crystallization is preferably 1 to 30 minutes, more preferably 5 to 20 minutes, and still more preferably 10 to 15 minutes.

In the present invention, the trivalent metal ion in the soluble trivalent metal source preferably includes one or more of Al ³⁺、Cr³⁺、Fe³⁺ and Sc ³⁺; the present invention is not particularly limited as to the specific kind of the soluble trivalent metal source, and may be, for example, one or more of sodium aluminate, ammonium aluminate and ferric chloride, using water-soluble salts of one or more of Al ³⁺、Cr³⁺、Fe³⁺ and Sc ³⁺, which are well known to those skilled in the art. In the present invention, the soluble trivalent metal source is preferably added in an amount of 0.1 to 2g/L, more preferably 0.2 to 1g/L, still more preferably 0.15 to 0.5g/L.

In the present invention, the crystallization-adsorption complexing temperature is preferably 20 to 50 ℃, more preferably 30 to 50 ℃, still more preferably 40 to 50 ℃; the crystallization-adsorption complexing time is preferably 10 to 60 minutes, more preferably 20 to 50 minutes, and even more preferably 30 to 40 minutes. In the crystallization-adsorption complexing process, hydrotalcite is generated in situ and radium and/or thorium in the wastewater are adsorbed and complexed.

The solid-liquid separation is not particularly limited, and may be performed by a solid-liquid separation method known to those skilled in the art, such as filtration, suction filtration, or centrifugal separation.

According to the generation mechanism and the generation rule of hydrotalcite, the invention determines the ionic radius required by hydrotalcite structure generation by adjusting the ionic proportion of different valence states, screens out high-efficiency hydrotalcite preparation materials and preparation processes, and realizes the removal of radioactive radium and thorium nuclides by utilizing a method for generating hydrotalcite in real time in wastewater. In addition, the invention adopts hydrotalcite in-situ generation technology to break through the single chemical reaction effect of the traditional precipitation method, and radium and thorium nuclides are removed by complexation in the hydrotalcite generation process, and the reaction is rapid and the separation effect is good.

For further explanation of the invention, a method for removing radium and/or thorium from hydrotalcite generated in situ in water is described in detail below in connection with the examples, but they should not be construed as limiting the scope of the invention.

In the following examples, the wastewater was a zirconium oxychloride production tail liquid.

Example 1

Under the condition of room temperature, the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium is regulated to 6.5 by using a reagent A (NaOH), the mixture is stirred for 5min after a reagent B is added, then a reagent C is added and stirred for 5min, then a reagent D is added, and the mixture is stirred for 40min at the temperature of 40 ℃ and filtered to obtain solid slag containing the thorium and filtrate respectively. The analysis results of the filtrate showed that thorium was 0.051mg/L and radium was 0.5Bq/L. The types and amounts of the reagents B to D added are shown in Table 1. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 1 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:MgCl₂	NaAlO₂
0.15G (total)	0.1g:0.9g	0.15g

Comparative example 1

Adding the reagent B into 1L tap water with the pH value of 6.5 at room temperature, stirring for 5min, adding the reagent C, stirring for 5min, adding the reagent D, stirring for 40min at 40 ℃, filtering, and drying the filter cake for 8h at 60 ℃ in a vacuum drying oven to obtain hydrotalcite. And (3) placing the hydrotalcite into 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium, stirring for 40min at 40 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed 0.096mg/L of thorium and 1.1Bq/L of radium. The types and amounts of the reagents B to D added are shown in Table 1. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

As can be seen from comparison between example 1 and comparative example 1, the method for removing hydrotalcite by in-situ formation of hydrotalcite in waste water is adopted, the proper valence complex formed by thorium radium can be directly reacted while hydrotalcite adsorbing material is in-situ formed, and simultaneously, the thorium radium is directly synthesized in waste water, and thorium radium nuclide is easier to enter into the vacancy of hydrotalcite in the synthesis process, so that the removal rate of radium is higher, the time consumption is shorter, and the treatment efficiency is high.

Example 2

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (NaOH), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.023mg/L and radium was 0.3Bq/L. The types and amounts of the reagents B to D are shown in Table 2. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 2 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:MnCl₂	NaAlO₂
0.15G (total)	0.2g:1.2g	0.15g

Example 3

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 9 by using a reagent A (NaOH), adding a reagent B, stirring for 5min, adding a reagent C, stirring for 5min, adding a reagent D, stirring for 40min at 40 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.076mg/L and radium was 0.2Bq/L. The types and amounts of the reagents B to D added are shown in Table 3. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 3 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:MgCl₂	NaAlO₂
0.15G (total)	0.1g:0.9g	0.15g

Example 4

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (NaOH), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.086mg/L and radium was 0.6Bq/L. The types and amounts of the reagents B to D added are shown in Table 4. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 4 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:NiCl₂	FeCl₃
0.15G (total)	0.15g:1.2g	0.15g

Example 5

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (NaOH), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.068mg/L and radium was 0.5Bq/L. The types and amounts of the reagents B to D are shown in Table 5. Wherein CaCO ₃:Ca(OH)₂ molar ratio in reagent B = 1:1.

TABLE 5 types and addition amounts of reagents B to D

Example 6

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (ammonia water with the mass concentration of 25%), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain solid slag containing thorium and filtrate respectively. The analysis of the filtrate showed 0.055mg/L of thorium and 0.76Bq/L of radium. The types and amounts of the reagents B to D are shown in Table 6. Wherein CaCO ₃:Ca(OH)₂ molar ratio in reagent B = 1:1.

TABLE 6 types and addition amounts of reagents B to D

B	C	D
			CaCO₃:Ca(OH)₂	NaOH:Mg(NO₃)₂	NH₄AlO₂
0.15G (total)	0.15g:1.2g	0.15g

Example 7

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (NaOH), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.049mg/L and radium was 0.52Bq/L. The types and amounts of the reagents B to D added are shown in Table 7. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 7 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:Mg₃(PO₄)₂	NaAlO₂
0.15G (total)	0.15g:1.2g	0.15g

Example 8

Adjusting the pH value of 1L of wastewater containing 3mg/L of thorium and 10Bq/L of radium to 6 by using a reagent A (NaOH), adding a reagent B, stirring for 10min, adding a reagent C, stirring for 10min, adding a reagent D, stirring for 30min at 50 ℃, and filtering to obtain radium-containing thorium solid slag and filtrate respectively. The analysis of the filtrate showed that thorium was 0.056mg/L and radium was 0.81Bq/L. The types and amounts of the reagents B to D added are shown in Table 8. Wherein MgCO ₃:Mg(OH)₂ molar ratio in reagent B = 1.5:1.

TABLE 8 types and addition amounts of reagents B to D

B	C	D
			MgCO₃:Mg(OH)₂	NaOH:Mg(NO₃)₂	FeCl₃
0.15G (total)	0.15g:1.2g	0.15g

While the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments of the invention can be made and still fall within the scope of the invention without undue effort.

Claims

1. A method for removing radium and/or thorium by in-situ generation of hydrotalcite in waste water comprises the following steps:

2. The method of claim 1, wherein the wastewater has a thorium content of 5mg/L or less and a radium content of 30Bq/L or less.

3. The method according to claim 1, wherein the pH adjusting agent used for the pH adjustment comprises one or more of sodium hydroxide, potassium hydroxide and ammonia water.

4. The method of claim 1, wherein the divalent metal ions in the insoluble divalent metal source comprise one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺;

the adding amount of the insoluble divalent metal source is 0.1-2 g/L.

5. The method according to any one of claims 1 to 4, wherein the nucleation is carried out at a temperature of 20 to 50 ℃ for a time of 1 to 30min.

6. The method of claim 1, wherein the divalent metal ions in the soluble divalent metal source comprise one or more of Mn ²⁺、Mg²⁺、Ca²⁺、Ni²⁺、Co²⁺、Zn²⁺、Fe²⁺ and Cu ²⁺.

7. The method according to claim 1, wherein the total addition amount of the alkali metal hydroxide and the soluble divalent metal source is 0.5 to 3g/L; the mass of the alkali metal hydroxide accounts for 10-30% of the total mass of the alkali metal hydroxide and the soluble divalent metal source.

8. The method according to claim 1, 6 or 7, wherein the pre-crystallization is carried out at a temperature of 20 to 50 ℃ for a time of 1 to 30min.

9. The method of claim 1, wherein the trivalent metal ions in the soluble trivalent metal source include one or more of Al ³⁺、Cr³⁺、Fe³⁺ and Sc ³⁺; the addition amount of the soluble trivalent metal source is 0.1-2 g/L.

10. The method according to claim 1 or 9, wherein the crystallization-adsorption complexation temperature is 20-50 ℃ for 10-60 min.